Authors: Ying Liu, Xiaorong Lai, Gang-Len Chang
Conference: the 2006 IEEE International Conference on Networking, Sensing and Control, 2006
One popular class of approaches to estimate freeway corridor travel time is based on measured or estimated speed data from roadside detectors. In most estimation practices, using either simulated or actual data, detectors are assumed to evenly distribute with a close spacing of around half mile. Unfortunately, this detector location scheme will be too costly for most freeway corridors under limited budget. To contend with this issue, this paper examines some widely used estimation algorithms under various traffic conditions with different detector spacing, and then proposes a set of strategies for locating detectors. Numerical results, based on traffic conditions on I-70 corridor of Maryland, have demonstrated the promising properties of our proposed strategies under recurrent congestion pattern.
Authors: Ying Liu, Nan Zou, and Gang-len Chang
Conference: the 2005 IEEE International Conference on Intelligent Transportation Systems
The consecutive hurricane attacks to US coastline have drawn significant attentions to evacuation operations related issues. To better prepare the state of Maryland for potential hurricanes, this study presents an emergency evacuation system that integrates both optimization and microscopic simulation methods. The optimization module applies a two-level process to generate the preliminary optimal control plans, which is based on a revised cell transmission formulation for large-scale network applications. Using the optimized results as the initial input, the simulation module takes into account various operational constraints and driver responses that are difficult to be captured realistically with mathematical formulations. The proposed system also features its flexibility for potential users to adjust the optimized plans in both the planning phase and real-time operations based on the results of simulation evaluation. The case study with the data from Ocean City, Maryland during hurricane attacks has demonstrated the potential of the proposed system for evacuation of traffic flows in large-scale networks within a given time window.
Authors: Nan Zou, Pei-Wei Lin, Gang-Len Chang, and Saed Rahwanji
Conference: The 6th Asia-Pacific Intelligent Transportation Systems Forum & Exhibitions, Taipei, Taiwan
Date: October, 2003
This paper presents a real-time incident management system that integrates the knowledge base with a microscopic traffic simulation model. The system consists of five modules: input module, knowledge-based module, prediction module, simulation module, and output module. The knowledge base is used to inventory the operational experience and traffic impact information associated with all recorded incidents. The prediction module is developed to predict the information of maximum queue length and incident duration predictions. The simulation module, developed with design plans for construction, contains traffic volumes and all detailed geometric features for both mainline segments and interchanges.
The proposed system will enable traffic control operators during the incident management period to perform two critical functions: (1) having an immediate estimate of the traffic impacts such as the queue length, average speed due to the detected incident; and (2) performing a subsequent detailed real-time analysis of network traffic conditions under various candidate incident management and/or control strategies with the simulation module.
The simulation results also offer the information between departure time and estimated travel time during the period of incident management. Furthermore, the system can also connect to the on-line detectors so that the real-time information can be used in the prediction and update of the simulation module.
To minimize both the learning and executing efforts of our target users, the integrated simulator is given a GIS-type of map features, allowing the operators to perform the input and output tasks through a user-friendly graphical interface.
Authors: Gang-Len Chang, Mark L. Franz, Yue Liu, Yang (Carl) Lu, and Ruihua Tao
Conference: 92th TRB Annual Meeting in 2013
This paper presents the design and evaluation of a dilemma zone protection system that utilizes the dynamic detection technology to track individual vehicles as they approach an intersection of interest. A high-speed rural intersection in Maryland experiencing a high frequency of crashes was selected for system installation and evaluation. Data collected from 3 sensors, designed specifically for tracking individual vehicles, were deployed along the target approach were used in real time to control the signal logic, providing green or all-red extensions when the pre-defined parameters of detected vehicles are met. To evaluate the performance of the system design and the effectiveness of the associated parameters, a field test was further conducted. The data analysis included the identification of falsely-called red extensions (related to efficiency) and missed red extensions (related to safety) to assess the overall performance of the newly installed system. The field observation results indicate that the newly designed dynamic dilemma zone protection system using an all-red extension offers distinct advantages over traditional systems by providing additional protection to high-speed vehicles even when they are in the “cannot go zone” and make an incorrect decision to go.
Authors: Andrey A. Petrov, Pei-Wei Lin, Nan Zou, Gang-Len Chang, and Jean Yves Point-Du-Jour
Conference: The 9th World Congress on Intelligent Transportation Systems, Chicago, Illinois
Date: October, 2002
The need to implement an effective Incident Management Systems (IMS) has received increasing attention from general public, media and policy makers, that in turn has required transportation agencies to perform a rigorous evaluation over any implemented plan. Since 1996, the Maryland State Highway Administration (MSHA) has conducted a comprehensive evaluation of its incident response and management program, named CHART. The evaluation consists of analysis of incident characteristics, evaluation of system efficiency and effectiveness, and estimation of benefits to the users. This paper is focused on presenting the results for the year 2000 CHART evaluation.
Authors: Yue Liu, Gang-Len Chang
Conference: The 19th International Symposium on Transportation and Traffic Theory
This paper presents a generalized diversion control model for freeway incident management that is capable of concurrently optimizing the detour rates and arterial signal timings over multiple roadway corridor segments between the freeway and its neighboring arterial. To capture various operational complexities due to the interactions between multiple diversions, this study has extended the model developed in our previous work (Liu et al., 2009), and integrated it in the overall corridor optimization process. The proposed generalized model based on reliable sensor data can produce the following three types of control parameters: 1) a set of critical upstream off-ramps and downstream on-ramps to be used for detour operations; 2) dynamic diversion rates and detour destinations for traffic at those critical upstream off-ramps within the control boundaries; and 3) arterial signal timings during the control time period. Numerical tests with a hypothetical corridor network have demonstrated the potential of the developed model for use on incident management.
Authors: Xiaorong Lai, Ying Liu, and Gang-Len Chang
Conference: the 11th IFAC symposium on Control in Transportation Systems, 2006
This paper presents a mixed-integer model for design of arterial signal control strategies during emergency evacuation. The proposed model can effectively take into account various complex operational issues such as critical intersection selection, demand rerouting, and signal timing. The control objective is to maximize the efficiency of the primary evacuation arterial, but not incur excessive waiting time and queues on its side streets. To evaluate the effectiveness of the proposed model under various demand levels and control objectives, this study has employed one major evacuation corridor in Washington D.C. as the target route for numerical experiments. The results of extensive simulation experiments reveal that the proposed method for signal optimization offers the potential for real-world applications.
Authors: Yue Liu, Gang-Len Chang and Ruihua Tao
Conference: 2007′ IEEE Conference on Intelligent Transportation Systems, Seattle, WA
This paper presents a video-based system for measuring dynamic dilemma zones at signalized intersections. The proposed system is cost-effective and sufficiently reliable for measuring various critical information associated driver behavior, including the speed before-and-after the yellow phase, the acceleration/deceleration rates and the approximate reaction time to an encountered yellow phase, and differences in driving patterns. Such information is critical for understanding the spatial distribution of dynamic dilemma zones and the design of strategies to improve intersection safety. This paper details the key components of the proposed system and the systematic procedures for field operations, data extraction, and system validation. The estimation of dilemma zones based on 1123 field observations of drivers’ responses via the proposed system at six intersections of high accident frequency are also reported in this paper.
Authors: Ying Liu, Peiwei Lin, Nan Zou, Gang-len Chang, and Jean Yves Point-Du-Jour
Conference: The 2004 IEEE International Conference on Networking, Sensing and Control, Taipei, Taiwan, March 2004.
The need to implement an effective Incident Management Systems (IMS) has received increasing attention by general public, media and policy makers, that in turn has required transportation agencies to perform a rigorous evaluation over any implemented plan. Since 1996, the Maryland State Highway Administration (MSHA) has conducted a comprehensive evaluation of its incident response and management program, named CHART. The evaluation study consisted of two phases. Whereas the focus of Phase 1 was on the reliable assess of system performance including incident detection, response, clearance and duration, the core of Phase 2 was to develop the methodology and to estimate resulting system benefits from data available in the CHART incident operations record.
Authors: Xianfeng Yang, Gang-Len Chang, Yang Lu, and Saed Rahwanji
Conference: 92th TRB Annual Meeting in 2013
Unconventional Design: CFI
Despite the increasing use of continuous flow intersections (CFI) to contend with the congestion caused by heavy through and left-turn traffic flows, a reliable and convenient tool for the traffic community to identify potential deficiencies for CFI’s geometry design are not available yet. This is due to the unique geometric feature of CFI which comprises one primary intersection and several crossover intersections. The interdependent relation between the traffic delays and queues at a CFI’s five closely-spaced intersections cannot be fully captured with the existing analysis models developed for conventional intersections. In response to such a need, this study presents a comprehensive analysis for the overall CFI delay, identifies the potential queue spillback locations, and develops a planning framework for CFI’s geometry designs. To facilitate the application of our proposed models, this paper also includes a case study of a CFI at intersection MD 4 and MD 235 conducted by Maryland State Highway Administration.